The invention relates, in general, to respirators and in particular to a new and useful circulation respirator for excess-pressure operation with a compressed gas source. The compressed gas source feeds an auxiliary arrangement which gives rise to a pressure increase in the respiratory circulation and also gives rise to a pressure increase in a measuring circuit connected to a sensor and controlling the auxiliary arrangement.
A similar circulation respirator is shown in DE 34 29 345 A1. In German reference DE 34 29 345 A1, a sensor connected to a measuring circuit monitors the fill level of the respiratory bag and is said to differentiate thereby between the inhalation phase and exhalation phase. The auxiliary arrangement is a cylinder-piston unit which is actuated by the compressed gas source. The auxiliary arrangement compresses the respiratory bag only during the inhalation phase and generates respiratory circulation excess pressure, which decreases in the exhalation phase. Consequently, during the exhalation phase no counter pressure is present, such a counter pressure places an additional unfavorable load on exhalation. In this prior known circulation respirator, however, it is desirable not to maintain the excess pressure during the entire inhalation phase because this represents unnecessary expenditures of energy for the fulfillment of the required functions. Moreover, determining the inhalation phase with the sensor coupled to the respiratory bag motion and scanning the position of the piston in the auxiliary device is difficult, and, in particular, no assurance is given that in the respiratory gas connection a positive pressure always obtains.